Liquid crystal display device

ABSTRACT

The technology presented herein has a feature of providing a liquid crystal display device of an excellent viewing angle characteristic and high brightness, including: liquid crystals containing polymerizable monomers between a first substrate with a pixel electrode having micro slits and a second substrate facing the first substrate; wherein the monomers are polymerizable with voltage applied to the liquid crystals; and an alignment orientation of the liquid crystals is controllable to a direction of extending the micro slit, wherein the pixel electrode includes: a direct coupling part electrically connected to a switching element; a capacitive coupling part electrically insulated from the switching element, and a space between the direct and capacitive coupling parts, wherein directions in which the micro slits are extended along the direct and capacitive coupling parts are orthogonal to each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/691,230, filed Jan. 21, 2010, which is a continuation of U.S.application Ser. No. 11/441,342, filed May 26, 2006, now U.S. Pat. No.7,656,474, which claims priority to Japanese Application 2005-158094,filed May 30, 2005, the entire contents of both being incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device for usein a display unit of electronic appliances.

2. Description of the Related Art

For a liquid crystal display device which can attain a wide viewingangle, a liquid crystal display device in MVA (Multi-domain VerticalAlignment) mode is known. The liquid crystal display device in the MVAmode has liquid crystals of negative dielectric anisotropy which aresealed between a pair of substrates, a vertical alignment film whichaligns liquid crystal molecules almost vertically with respect to thesubstrate surface, and an alignment regulating structure which regulatesthe alignment orientation of liquid crystal molecules. For the alignmentregulating structure, a linear protrusion formed of a dielectric and anopen part (main slit) of an electrode are used. When voltage is applied,the liquid crystal molecules are tilted in the direction vertical to thedirection in which the alignment regulating structure is extended. Thealignment regulating structure is used to provide a plurality of areasin a single pixel, the area being different in the alignment orientationof the liquid crystal molecules, and thus a wide viewing angle can beobtained. However, in this liquid crystal display device, since theprotrusion and the main slit are formed in the pixel area, the apertureratio is lower than ones in the TN (Twisted Nematic) mode etc., and thusthe light transmittance is reduced.

FIG. 34 shows the pixel structure of a liquid crystal display device inthe MVA mode in which the aperture ratio is improved. FIG. 35 shows thesectional structure of the liquid crystal display device sectioned atline A-A shown in FIG. 34. As shown in FIGS. 34 and 35, the liquidcrystal display device has a pair of substrates 102 and 104, and liquidcrystals 106 which are sealed between the substrates 102 and 104. On thesubstrate 102, a gate bus line 112 and a drain bus line 114 are formedas they intersect with each other through an insulating film. A pixelarea is defined by the gate bus line 112 and the drain bus line 114.Near the position at which the gate bus line 112 and the drain bus line114 intersect with each other, a TFT 120 is formed. In each of the pixelareas, a pixel electrode 116 is formed. The pixel electrode 116 isformed with a micro slit 116 d which is cut from a rim. The alignmentorientation of the liquid crystals molecules 108 is controlled by anoblique electric field at the end of the pixel electrode 116. In thisliquid crystal display device, a high aperture ratio and lighttransmittance can be obtained because the linear protrusion and the mainslit are not formed in the pixel area. However, since the micro slit 116d has weaker alignment control than that of the linear protrusion andthe main slit, the liquid crystal display device has a long responsetime of the liquid crystals, and the alignment is easily disturbed by afinger press or so.

Then, a polymer sustained alignment (PSA) technique is introduced inwhich polymerizable monomers are mixed in liquid crystals to polymerizethe monomers in the state in which voltage is applied to the liquidcrystals and thus the orientation in which the liquid crystals aretilted is stored (for example, see Patent Document 1). In the liquidcrystal display device using the PSA technique, a polymerized film whichstores the alignment orientation of the liquid crystals is formed on theinterface of an alignment film. Thus, strong alignment control isobtained, and it can be ensured that liquid crystals molecules 108 aretilted in the direction in parallel with the micro slit 116 d.

However, in a liquid crystal display device in the VA mode in which thebirefringence property of the liquid crystals vertically aligned is usedfor switching light, the phase difference caused by birefringence in theoblique direction is greatly shifted from that in the front direction,and thus display can have a white patch when a screen is viewed from theoblique direction. This is a phenomenon called washout in which the graylevel brightness characteristic, that is, the γ characteristic isshifted from a set value in all the gray scale levels more or less.

For a scheme to improve washout, there is a technique in which a singlepixel is split into a plurality of areas to vary the voltage applied toliquid crystals in a single pixel. This is a technique in which thealignment orientation of liquid crystals is varied in the azimuth angledirection as well as in the polar angle direction to reduce the shift ofthe phase difference between the oblique direction and the frontdirection. More specifically, the alignment orientation of liquidcrystals in a single pixel is split in the polar angle direction as wellas in the azimuth angle direction to average the variation in the phasedifference in the polar angle direction as well, and thus a white patchcan be reduced.

FIG. 36 shows the pixel structure of a liquid crystal display devicewhich implements the technique above. As shown in FIG. 36, a pixelelectrode in each of pixel areas has a direct coupling part 116 a whichis directly connected to a source electrode of a TFT 120, a capacitivecoupling part 116 b which is indirectly connected to the sourceelectrode through capacitance formed between it and a controlcapacitance electrode 125, and a space 117 which isolates them. Thedirect coupling part 116 a and the capacitive coupling part 116 b eachhave a plurality of line electrodes (width l) which is extended in apredetermined direction, and a micro slit (width s) which is between theadjacent line electrodes. Near the space 117, the micro slits of thedirect coupling part 116 a and the micro slit of the capacitive couplingpart 116 b are extended almost in parallel with each other. In theconfiguration shown in FIG. 36, the voltage applied to the liquidcrystals are varied between the direct coupling part 116 a and thecapacitive coupling part 116 b to obtain an effect to reduce a whitepatch.

However, this mode has a problem that a potential difference isgenerated between the direct coupling part 116 a and the capacitivecoupling part 116 b and that potential difference causes a shift of thealignment orientation of liquid crystals in the space 117 from theorientation defined by the micro slit of the pixel electrode. FIG. 37Ashows the pixel electrode structure near the space 117. FIG. 37B showsthe simulation result of the display state of a pixel. As shown in FIG.37A, since a smaller voltage is applied to the capacitive coupling part116 b when it is driven than that to the direct coupling part 116 a, theelectrode end of the direct coupling part 116 a works just like a mainslit, and the tilt orientation of the liquid crystal molecules istemporarily vertical to the electrode end of the direct coupling part116 a. On this account, the alignment at the direct coupling part 116 aand the capacitive coupling part 116 b near the space 117 is greatlydisturbed. This phenomenon is called azimuth angle (φ) fluctuations.When the φ fluctuations occur, the birefringence properties of theliquid crystals are locally reduced to generate a dark line as shown inFIG. 37B. Thus, the light transmittance of a pixel is decreased. Inaddition, the shift of the alignment orientation of liquid crystals alsoaffects the viewing angle characteristic to reduce the effect thatimproves the white patch described above as well. In order to reduce theinfluence on the viewing angle characteristic, it is necessary to shieldlight in the space 117 between the direct coupling part 116 a and thecapacitive coupling part 116 b by a black matrix (BM). On this account,a problem arises that the light transmittance of a pixel is furtherdecreased.

Patent Document 1: JP-A-2003-149647

Patent Document 2: JP-A-2003-177408

SUMMARY OF THE INVENTION

An object of the invention is to provide a liquid crystal display devicewhich can attain an excellent viewing angle characteristic and highbrightness.

The object is achieved by a liquid crystal display device including:sandwiching liquid crystals containing polymerizable monomers between afirst substrate provided with a pixel electrode having a micro slit anda second substrate facing the first substrate; polymerizing the monomersas voltage is applied to the liquid crystals; and controlling analignment orientation of the liquid crystals to a direction in which themicro slit is extended, wherein the pixel electrode includes: a directcoupling part which is electrically connected to a switching element; acapacitive coupling part which is electrically insulated from theswitching element, and which forms capacitance with a controlcapacitance electrode which has a same potential as that of a sourceelectrode of the switching element; and a space which is between thedirect coupling part and the capacitive coupling part, whereindirections in which the micro slit is extended in the adjacent directcoupling part and in the capacitive coupling part are orthogonal to eachother.

In the liquid crystal display device according to the invention, thespace is in a linear form.

In the liquid crystal display device according to the invention, alongitudinal direction of the space is almost in parallel with adirection in which the micro slit is extended in the capacitive couplingpart.

In the liquid crystal display device according to the invention, a widthof the space is almost the same as a width of the micro slit.

In the liquid crystal display device according to the invention, thedirect coupling part and the capacitive coupling part each have foursplit areas in which the micro slit is extended in directions differentfrom each other, and the control capacitance electrode and the storagecapacitor electrode are disposed along a border between the split areas.

In the liquid crystal display device according to the invention, theliquid crystals have negative dielectric anisotropy, and are verticallyaligned when voltage is not applied.

According to the invention, a liquid crystal display device can beimplemented which can obtain an excellent viewing angle characteristicand high brightness.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the invention can be readily understood by consideringthe following detailed description in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram illustrating the schematic configuration of a liquidcrystal display device according to a first embodiment of the invention;

FIG. 2 is a diagram illustrating the principle of the liquid crystaldisplay device according to the first embodiment of the invention;

FIG. 3 is a diagram illustrating a comparative example of a liquidcrystal display device according to the first embodiment of theinvention;

FIG. 4 is a diagram illustrating the single pixel configuration of aliquid crystal display device according to the example 1-1 of the firstembodiment of the invention;

FIG. 5 is a diagram illustrating the single pixel configuration of aliquid crystal display device according to the example 1-2 of the firstembodiment of the invention;

FIG. 6 is a diagram illustrating the simulation result of the displaystate of a single pixel in the liquid crystal display device accordingto the example 1-2 of the first embodiment of the invention;

FIG. 7 is a diagram illustrating the configuration of six pixels in theliquid crystal display device according to the example 1-2 of the firstembodiment of the invention;

FIG. 8 is a diagram illustrating a modification of the configuration ofthe liquid crystal display device according to the example 1-2 of thefirst embodiment of the invention;

FIG. 9 is a diagram illustrating a problem of a liquid crystal displaydevice having the pixel structure shown in FIG. 36;

FIG. 10 is a graph illustrating the gray level γ characteristic in theoblique direction;

FIG. 11 is a diagram illustrating a first basic pixel configuration of aliquid crystal display device according to a second embodiment of theinvention;

FIG. 12 is a cross section illustrating the first basic pixelconfiguration of the liquid crystal display device according to thesecond embodiment of the invention;

FIG. 13 is a cross section illustrating the first basic pixelconfiguration of the liquid crystal display device according to thesecond embodiment of the invention;

FIG. 14 is a diagram illustrating a second basic pixel configuration ofthe liquid crystal display device according to the second embodiment ofthe invention;

FIG. 15 is a diagram illustrating the pixel configuration of a liquidcrystal display device according to the example 2-1 of the secondembodiment of the invention;

FIG. 16 is a diagram illustrating the pixel alignment of the liquidcrystal display device according to the example 2-1 of the secondembodiment of the invention;

FIG. 17 is a diagram illustrating the pixel configuration of a liquidcrystal display device according to the comparative example 2-1 of thesecond embodiment of the invention;

FIG. 18 is a diagram illustrating the pixel alignment of the liquidcrystal display device according to the comparative example 2-1 of thesecond embodiment of the invention;

FIG. 19 is a diagram illustrating the pixel configuration of liquidcrystal display device according to the example 2-2 of the secondembodiment of the invention;

FIG. 20 is a diagram illustrating the pixel alignment of the liquidcrystal display device according to the example 2-2 of the secondembodiment of the invention;

FIG. 21 is a graph illustrating the azimuth angle distribution of thealignment of liquid crystals of the liquid crystal display device;

FIG. 22 is a graph illustrating the gray level γ characteristic of theliquid crystal display device in the oblique direction;

FIG. 23 is a diagram illustrating the pixel configuration of a liquidcrystal display device according to the example 2-3 of the secondembodiment of the invention;

FIG. 24 is a diagram illustrating the pixel alignment of the liquidcrystal display device according to the example 2-3 of the secondembodiment of the invention;

FIG. 25 is a graph illustrating the azimuth angle distribution of thealignment of liquid crystals of a liquid crystal display device;

FIG. 26 is a graph illustrating the gray level γ characteristic of theliquid crystal display device in the oblique direction;

FIG. 27 is a diagram illustrating the pixel configuration of a liquidcrystal display device;

FIGS. 28A to 28C are diagrams schematically illustrating process stepsof polymerizing monomers;

FIG. 29 is a diagram illustrating the basic pixel configuration of aliquid crystal display device according to a third embodiment of theinvention;

FIGS. 30A and 30B are diagrams illustrating the alignment state near thealignment split area of a liquid crystal display panel according toexample 3-1 of the third embodiment of the invention;

FIG. 31 is a diagram illustrating the relationship between an electrodeopen part and an equal potential line;

FIG. 32 is a diagram illustrating the pixel configuration of a liquidcrystal display panel according to the example 3-3 of the thirdembodiment of the invention;

FIG. 33 is a diagram illustrating the pixel configuration of the liquidcrystal display panel according to the example 3-3 of the thirdembodiment of the invention;

FIG. 34 is a diagram illustrating the pixel structure of a liquidcrystal display device in the MVA mode;

FIG. 35 is a cross section illustrating the pixel structure of theliquid crystal display device in the MVA mode;

FIG. 36 is a diagram illustrating the pixel structure of the liquidcrystal display device in the MVA mode; and

FIGS. 37A and 37B are diagrams illustrating a problem of the liquidcrystal display device in the MVA mode.

DESCRIPTION OF THE PREFERRED EMBODIMENT First Embodiment

A liquid crystal display device according to a first embodiment of theinvention will be described with reference to FIGS. 1 to 8. FIG. 1 showsthe schematic configuration of the liquid crystal display deviceaccording to this embodiment. As shown in FIG. 1, the liquid crystaldisplay device has a TFT substrate 2 provided with a gate bus line and adrain bus line which are formed as they intersect with each otherthrough an insulating film, and a TFT (switching element) and a pixelelectrode which are formed at every pixel. In addition, the liquidcrystal display device has a opposite substrate 4 on which a colorfilter (CF) and a common electrode are formed, and which is disposedfacing the TFT substrate 2. Between the substrates 2 and 4, liquidcrystals 6 are sealed (not shown in FIG. 1).

To the TFT substrate 2, drive circuits are connected: a gate bus linedrive circuit 80 on which a driver IC is mounted to drive a plurality ofthe gate bus lines, and a drain bus line drive circuit 82 on which adriver IC is mounted to drive a plurality of the drain bus lines. Thesedrive circuits 80 and 82 output a scanning signal and a data signal to apredetermined gate bus line or drain bus line based on a predeterminedsignal outputted from a control circuit 84. A polarizer 87 is arrangedon the surface opposite to the surface of the TFT substrate 2 on whichTFT elements are formed, and a polarizer 86 is disposed in crossed Nicolwith the polarizer 87 on the surface opposite to the surface of theopposite substrate 4 on which the common electrode is formed. Abacklight unit 88 is placed on the surface of the polarizer 87 oppositeto the TFT substrate 2.

In the embodiment, the combination of the alignment orientations ofliquid crystals is optimized in a direct coupling part and a capacitivecoupling part in a pixel area. FIG. 2 is a diagram illustrating theprinciple of the liquid crystal display device according to theembodiment. As shown in FIG. 2, in the embodiment, a pixel electrode 16has a direct coupling part 16 a which is electrically connected to asource electrode of the TFT, a capacitive coupling part 16 b which iselectrically insulated from the TFT and forms capacitance with a controlcapacitance electrode which has the same potential as that of the sourceelectrode of the TFT, and a space 17 which is between the directcoupling part 16 a and the capacitive coupling part 16 b. For example,the pixel electrode 16 is formed of a transparent conductive film suchas ITO. In addition, the direct coupling part 16 a of the pixelelectrode 16 has a plurality of micro slits 30 a, and the capacitivecoupling part 16 b has a plurality of micro slits 30 b. In the adjacentdirect coupling part 16 a and the capacitive coupling part 16 b adjacentto each other through the space 17, the micro slits 30 a and 30 b arealmost orthogonal to each other. Furthermore, the space (the area withno ITO) 17 which is the border between the direct coupling part 16 a andthe capacitive coupling part 16 b is formed in a linear form having astraight part or a bend. The longitudinal direction of the space 17 isalmost in parallel with the direction in which the micro slit 30 b ofthe capacitive coupling part 16 b is extended, and is almost verticallyto the direction in which the micro slit 30 a of the direct couplingpart 16 a is extended.

In the configuration shown in FIG. 2, the alignment orientation of theliquid crystal molecules between the direct coupling part 16 a and thecapacitive coupling part 16 b is done by the rotation at an angle of 90degrees, and only a single dark line is generated. In addition, sincethe tilt orientation of the liquid crystal molecules is matched with thealignment orientation of the direct coupling part 16 a when the end ofthe direct coupling part 16 a of the pixel electrode 16 works just likea main slit at the time when voltage is applied, the alignmentorientation of liquid crystals becomes stabilized, and the φfluctuations do not occur. Therefore, the alignment of liquid crystalsin the space 17 between the direct coupling part 16 a and the capacitivecoupling part 16 b is excellent overall, the dark lines are few, thelight transmittance is high, and an effect to sufficiently improve awhite patch can be obtained as well.

On the other hand, in the case in which the layout of the directcoupling part 16 a and the capacitive coupling part 16 b is in reverseas a comparative example shown in FIG. 3, the edge of a direct couplingpart 16 a works to disturb the alignment, and thus the dark lines areincreased. Therefore, an excellent alignment can be obtained only in thecase of the layout of the direct coupling part 16 a and the capacitivecoupling part 16 b as shown in FIG. 2.

In the embodiment, liquid crystals containing monomers are supportedbetween the substrates 2 and 4, and the monomers are polymerized in thestate in which voltage is applied to the liquid crystals. Accordingly,the alignment orientation of liquid crystals is controlled by thedirection in which the micro slits 30 a and 30 b are extended. Here, theliquid crystals have negative dielectric anisotropy, and are verticallyaligned when voltage is not applied.

Hereinafter, the liquid crystal display device according to theembodiment will be described more specifically with examples.

Example 1-1

FIG. 4 shows the single pixel configuration of a liquid crystal displaydevice according to the example 1-1 of the embodiment. As shown in FIG.4, a pixel area is defined by a gate bus line 12 and a drain bus line 14which intersect with each other through an insulating film. In theexample, a direct coupling part 16 a is disposed at the center of thepixel area, and a capacitive coupling part 16 b is disposed at the upperpart and the lower part in the pixel area as they sandwich the directcoupling part 16 a in the drawing. The direct coupling part 16 a iselectrically connected to a source electrode of a TFT 20 through acontact hole and a control capacitance electrode 25. The capacitivecoupling part 16 b forms capacitance with the control capacitanceelectrode 25 which has the same potential as that of the sourceelectrode of the TFT 20. In the example, alignment irregularities arebasically small in a space 17 between the direct coupling part 16 a andthe capacitive coupling part 16 b, and on the contrary, the alignmentirregularities sometimes occur when a storage capacitor bus line 18, astorage capacitor electrode, etc. are disposed for light shielding.Therefore, the storage capacitor bus line and the storage capacitorelectrode were not disposed there, and they were disposed in the area inwhich alignment irregularities were more likely to occur (the centerpart of the pixel in this example). The width of the space 17 is 3 to 5μm, which is almost the same as the width of the micro slits 30 a and 30b.

Example 1-2

FIG. 5A shows the single pixel configuration of a liquid crystal displaydevice according to the example 1-2 of the embodiment, and FIG. 5B showsthe layout of a storage capacitor bus line 18, a storage capacitorelectrode 19 and a control capacitance electrode 25 in that pixel. FIG.6 shows the simulation result of the display state of a pixel in theliquid crystal display device according to the embodiment. In theexample 1-1 above, the pixel area is split into three parts, a singledirect coupling part 16 a and two capacitive coupling parts 16 b.Therefore, five alignment split lines exist vertically including thespace 17. Since these parts become the dark lines, a fewer number ofalignment split lines is preferable. As shown in FIGS. 5A, 5B and 6, inthe example, a direct coupling part 16 a is disposed in the upper pixelarea, and a capacitive coupling part 16 b is disposed in the lower pixelarea. The pixel area was split into two parts to reduce the number ofthe alignment split lines to three. Therefore, the pixel structure of afewer number of dark lines and high brightness is obtained.

The direct coupling part 16 a and the capacitive coupling part 16 b eachhave four split areas in which micro slits are extended in directionsdifferent from each other (for example, in four orthogonal directions).The border between the split areas including a space 17 between thedirect coupling part 16 a and the capacitive coupling part 16 b is thealignment split line. Since it is preferable not to dispose a storagecapacitor electrode 19 etc. in the space 17, a control capacitanceelectrode 25, a storage capacitor electrode 19 and a storage capacitorbus line 18 are disposed in a capital I shape so that they are along thealignment split lines other than that. This is done also for securing anarea which is necessary for an auxiliary capacitance electrode. Forexample, the width of the storage capacitor bus line 18 is 4 μm, and thewidth of the control capacitance electrode 25 is 8 μm. The storagecapacitor electrode 19 etc. which reduce the aperture ratio as the lightshielding area are disposed so as to overlap with the alignment splitline which is basically dark, and thus a high light transmittance can beobtained.

Example 1-3

FIG. 7 shows the configuration of six pixels of a liquid crystal displaydevice according to the example 1-3 of the embodiment. As shown in FIG.7, in the example, a structure was formed in which the form of the edgeof a pixel electrode 16 is optimized, and all the cuts of a directcoupling part 16 a and a capacitive coupling part 16 b are orthogonal tothe direction in which a micro slit is extended. In addition, in theexample, a gate bus line 12 also serves as a storage capacitor bus line18. According to the example, the alignment of the pixel edge becomesexcellent, and the brightness and the viewing angle characteristic areboth improved.

FIG. 8 shows a modification of the configuration of the liquid crystaldisplay device according to the embodiment. As shown in FIG. 8, in themodification, in order to secure storage capacitor, a storage capacitorbranch wiring 18′ which is branched from the gate bus line 12, a storagecapacitor electrode 19 and a control capacitance electrode 25 areextended around the pixel.

Second Embodiment

Next, a liquid crystal display device according to a second embodimentof the invention will be described with reference to FIGS. 9 to 26. Asdescribed above, in the liquid crystal display device in the VA mode,the phase difference caused by birefringence in the oblique direction isgreatly shifted from that in the front direction. On this account, thedisplay color is shifted between the time when a screen is viewed fromthe front direction and the time when the screen is viewed from theoblique direction. This is a phenomenon called a color shift. The colorshift occurs by shifting the gray level brightness characteristic in theoblique direction, that is, the y characteristic from a characteristicset value in the front direction.

This problem can be improved by the liquid crystal display device havingthe pixel structure shown in FIG. 36. The alignment orientation ofliquid crystals in a single pixel is split in the azimuth angledirection as well as in the polar angle direction, and thus thevariation in the phase difference in the polar angle direction is alsoaveraged to reduce the color shift.

However, in this mode, there is a problem that a potential difference isgenerated between the direct coupling part 116 a having a larger appliedvoltage and the capacitive coupling part 116 b having a smaller appliedvoltage and that potential difference causes the alignment orientationof liquid crystals in the space 117 to shift from the orientationcontrolled by the micro slit 116 d of the pixel electrode 116. FIG. 9schematically shows the alignment of liquid crystals. As shown in FIG.9, in the border area between a direct coupling part 116 a and acapacitive coupling part 116 b, the alignment of liquid crystals isgreatly disturbed to generate a dark line caused by the φ fluctuations.When the dark line is generated in the display area, not only thetransmittance is reduced but the color shift becomes greater.

FIG. 10 shows a graph illustrating the gray level γ characteristic inthe oblique direction. As shown in FIG. 10, the capacitive coupling part116 b is disposed in the pixel to make the γ value in the range of thehalftone levels close to a set value on the front side, and the colorshift in the halftone levels is improved. However, since the γ value inthe range of high gray levels is shifted from the set value on the frontside, a problem arises that the color shift in the high gray levels isgreat.

The embodiment is made to solve the problem, and an object is to providea bright liquid crystal display device having a small color shift.

The object is achieved by a liquid crystal display device including:sandwiching liquid crystals containing polymerizable monomers between afirst substrate provided with a pixel electrode having a micro slit anda second substrate facing the first substrate; polymerizing the monomersas voltage is applied to the liquid crystals; and controlling analignment orientation of the liquid crystals to a direction in which themicro slit is extended, wherein the pixel electrode includes: a directcoupling part which is electrically connected to a switching element;and a capacitive coupling part which is electrically insulated from theswitching element, and which forms capacitance with a controlcapacitance electrode which has a same potential as that of a sourceelectrode of the switching element, wherein the direct coupling part andthe capacitive coupling part are isolated from each other at a border ofthe control capacitance electrode and/or a storage capacitor bus line.

In the liquid crystal display device according to the embodiment, in anarea in which the control capacitance electrode and the storagecapacitor bus line overlap with each other, the control capacitanceelectrode is disposed inside the storage capacitor bus line.

In the liquid crystal display device according to the embodiment, in anarea in which the control capacitance electrode and the pixel electrodeoverlap with each other, the control capacitance electrode is disposedinside the pixel electrode.

In the liquid crystal display device according to the embodiment, thealignment orientation of the liquid crystals is split at a border of thecontrol capacitance electrode or the storage capacitor bus line.

In the liquid crystal display device according to the embodiment, thedirection in which the micro slit is extended as adjacent to the gatebus line or the drain bus line is almost vertical to a direction inwhich the gate bus line or the drain bus line is extended.

In the liquid crystal display device according to the embodiment, thedirect coupling part of the pixel electrode is disposed on a sourceelectrode side of the switching element.

In the liquid crystal display device according to the embodiment, thepixel electrode is not formed in an area facing a resin spacer which isformed on the second substrate.

In the liquid crystal display device according to the embodiment, lightis shielded in a part adjacent to the control capacitance electrodeand/or the storage capacitor bus line in the pixel electrode by a blackmatrix which is formed on the second substrate.

FIG. 11 shows a first basic pixel configuration of the liquid crystaldisplay device according to the embodiment. FIG. 12 shows the sectionalconfiguration of the liquid crystal display device sectioned at line B-Bshown in FIG. 11, and FIG. 13 shows the sectional configuration of theliquid crystal display device sectioned at line C-C shown in FIG. 11. Asshown in FIGS. 11 to 13, the liquid crystal display device has a TFTsubstrate 2, a opposite substrate 4, and liquid crystals 6 which aresealed between the substrates 2 and 4. On the interface between thesubstrates sandwiching the liquid crystals 6, a polymerized film isformed which is formed by polymerizing monomers mixed in the liquidcrystals 6 with voltage applied. A pixel electrode 16 formed on the TFTsubstrate 2 has a direct coupling part 16 a which is electricallyconnected to a source electrode of a TFT 20, and a capacitive couplingpart 16 b which forms capacitance with a control capacitance electrode25 which is electrically connected to the source electrode. The directcoupling part 16 a and the capacitive coupling part 16 b are isolatedfrom each other at the border of a storage capacitor part 21. The directcoupling part 16 a is formed with a micro slit 30 a, and the capacitivecoupling part 16 b is formed with a micro slit 30 b. The alignmentorientation of the liquid crystals 6 is controlled by the direction inparallel with the direction in which the micro slits 30 a and 30 b areextended.

In addition, preferably, in the area in which the control capacitanceelectrode (storage capacitor electrode) 25 and a storage capacitor busline 18 overlap with each other, the control capacitance electrode 25 isdisposed inside the storage capacitor the bus line 18, and in the areain which the control capacitance electrode 25 and the pixel electrode 16overlap with each other, the control capacitance electrode 25 isdisposed inside the pixel electrode 16, and the alignment orientation ofthe liquid crystals 6 is split at the border of the control capacitanceelectrode 25 or the storage capacitor bus line 18.

FIG. 14 shows a second basic pixel configuration of the liquid crystaldisplay device according to the embodiment. As shown in FIG. 14, thedirection in which the micro slits 30 a and 30 b are extended asadjacent to a gate bus line 12 or a drain bus line 14 is almost verticalto the direction in which the gate bus line 12 or the drain bus line 14is extended.

As shown in FIG. 14, the direct coupling part 16 a and the capacitivecoupling part 16 b are isolated from each other at the border of thestorage capacitor part 21 to eliminate a dark line caused by the φfluctuations generated in the border area between the direct couplingpart 16 a and the capacitive coupling part 16 b. More specifically, thedirect coupling part 16 a having a greater applied voltage is isolatedfrom the capacitive coupling part 16 b having a smaller applied voltageat the border of the storage capacitor part 21, and thus the dark linecaused by the φ fluctuations is fixed to the storage capacitor part 21to prevent the dark line from being generated in the display area.

In addition, preferably as shown in FIG. 12, in the area in which thecontrol capacitance electrode 25 and the storage capacitor bus line 18overlap with each other, the control capacitance electrode 25 is formedinside the storage capacitor bus line 18. Accordingly, the obliqueelectric field of the control capacitance electrode 25 can be cancelledat the storage capacitor bus line 18, and thus the alignment orientationof the liquid crystals 6 near the storage capacitor part 21 can bealigned with the orientation controlled by the micro slits 30 a and 30b. To the contrary, when the control capacitance electrode 25 is formedoutside the storage capacitor bus line 18, the oblique electric field ofthe control capacitance electrode 25 and the oblique electric field ofthe pixel electrode 16 interfere with each other near the storagecapacitor part 21, and the alignment orientation of the liquid crystals6 is shifted from the orientation controlled by the micro slits 30 a and30 b. It causes no problem when the distance between the controlcapacitance electrode 25 and the pixel electrode 16 is sufficientlylong, but in this case, the transmittance is reduced.

In addition, preferably as shown in FIG. 13, in the area in which thecontrol capacitance electrode 25 and the pixel electrode 16 overlap witheach other, the control capacitance electrode 25 is formed inside thepixel electrode 16. Accordingly, the oblique electric field of thecontrol capacitance electrode 25 can be cancelled at the pixel electrode16, and thus the alignment orientation of the liquid crystals 6 near abackbone part 26 formed by the control capacitance electrode 25 and thepixel electrode 16 can be aligned with the orientation controlled by themicro slits 30 a and 30 b. To the contrary, when the control capacitanceelectrode 25 is formed outside the pixel electrode 16, the obliqueelectric field of the control capacitance electrode 25 and the obliqueelectric field of the pixel electrode 16 interfere with each other, andthe alignment orientation of the liquid crystals 6 is shifted from theorientation controlled by the micro slits 30 a and 30 b.

In addition, preferably as shown in FIG. 11, the alignment orientationof the liquid crystals 6 is split at the border of the controlcapacitance electrode 25 or the storage capacitor bus line 18.Accordingly, light at the alignment border of the liquid crystals 6 inwhich the φ fluctuations are relatively great can be shielded by thecontrol capacitance electrode 25 or the storage capacitor bus line 18,and thus a color shift can be made smaller.

Furthermore, as shown in FIG. 14, the direction in which the micro slits30 a and 30 b are extended as adjacent to the gate bus line 12 or thedrain bus line 14 is made almost vertical to the direction in which thegate bus line 12 or the drain bus line 14 is extended. Accordingly, thedirection of the oblique electric field of the pixel electrode 16 andthe direction of the oblique electric field of the pixel space can bemade the same, and thus the alignment orientation of the liquid crystals6 near the gate bus line 12 and the drain bus line 14 can be alignedwith the orientation controlled by the micro slits 30 a and 30 b.

Hereinafter, the liquid crystal display device according to theembodiment will be described more specifically with examples.

Example 2-1

FIG. 15 shows the pixel configuration of a liquid crystal display deviceaccording to the example 2-1 of the embodiment, and FIG. 16 shows thepixel alignment of the liquid crystal display device according to theexample. FIG. 17 shows the pixel configuration of a liquid crystaldisplay device according to the comparative example 2-1, and FIG. 18shows the pixel alignment of the liquid crystal display device accordingto the comparative example 2-1. As shown in FIG. 17, in the liquidcrystal display device according to the comparative example, a directcoupling part 16 a and a capacitive coupling part 16 b are not isolatedfrom each other at the border of a storage capacitor part 21. A pixelelectrode 16 is formed to have a line width of 6 μm, and has micro slits30 a and 30 b which are extended at azimuth angles of 45, 135, 225 and315 degrees at a slit width of 3.5 μm. Voltage is applied to liquidcrystals 6 to polymerize monomers to control the alignment of the liquidcrystals 6 in the direction in which the micro slits 30 a and 30 b areextended. Here, the liquid crystals 6 have negative dielectricanisotropy, and are aligned vertically when voltage is not applied. Inaddition, in the case in which the liquid crystals 6 have positivedielectric anisotropy and are aligned horizontally when voltage is notapplied, the applied voltage in polymerizing monomers cannot be madegreater. Therefore, it becomes difficult to control the alignmentorientation of the liquid crystals 6 to the direction in which the microslits 30 a and 30 b are extended.

In addition, the pixel electrode 16 is formed of a direct coupling part16 a which is electrically connected to a source electrode 22 of a TFT20, and a capacitive coupling part 16 b which is electrically insulatedfrom the TFT 20, and which forms capacitance with a control capacitanceelectrode 25 which is electrically connected to the source electrode 22.The direct coupling part 16 a is electrically connected to the TFT 20through a contact hole 24 which is formed at the center part of thepixel area.

In the pixel layout of the comparative example, a direct coupling part16 a and a capacitive coupling part 16 b are not isolated from eachother at the border of a storage capacitor part 21. Therefore, as thepixel alignment as shown in FIG. 18, a potential difference is generatedin the border area between the direct coupling part 16 a having agreater applied voltage and the capacitive coupling part 16 b having asmaller applied voltage, and the alignment orientation of the liquidcrystals 6 is greatly shifted from the orientation controlled by themicro slits 30 a and 30 b to generate a dark line caused by the φfluctuations.

On the other hand, in the pixel layout of the example shown in FIG. 15,since the direct coupling part 16 a and the capacitive coupling part 16b are isolated from each other at the border of the storage capacitorpart 21, the dark line caused by the φ fluctuations is fixed to thestorage capacitor part 21 to eliminate it from the display area as thepixel alignment shown in FIG. 16. In addition, in the pixel layout shownin FIG. 15,

(1) in the area in which the control capacitance electrode 25 and astorage capacitor bus line 18 overlap with each other, the controlcapacitance electrode 25 is disposed inside the storage capacitor busline 18;(2) in the area in which the control capacitance electrode 25 and thepixel electrode 16 overlap with each other, the control capacitanceelectrode 25 is disposed inside the pixel electrode 16;(3) the alignment orientation of the liquid crystals 6 is split at theborder of the control capacitance electrode 25 or the storage capacitorbus line 18;(4) the direct coupling part 16 a of the pixel electrode is disposed onthe source electrode 22 side of the TFT 20 in the pixel area; and(5) the pixel electrode 16 is not formed in the area facing a resinspacer 52 which is formed on a opposite substrate 4.

The cross section near the capacitive coupling part 16 b in the pixellayout shown in FIG. 15 is as shown in FIG. 12. As shown in FIG. 12, ona glass substrate 10 of a TFT substrate 2, the storage capacitor busline 18, a gate insulating film 31, the control capacitance electrode25, a final protective film 32, the pixel electrode 16 (direct couplingpart 16 a), and a vertical alignment film 33 are sequentially formed.The control capacitance electrode 25 is electrically connected to thepixel electrode 16 through a contact hole 24. On the other hand, on aglass substrate 11 of the opposite substrate 4, a black matrix (BM) 50,a color filter layer 40, a common electrode 41, and a vertical alignmentfilm 33 are sequentially formed.

As in (1) above, the control capacitance electrode 25 is formed insidethe storage capacitor bus line 18, and thus the oblique electric fieldof the control capacitance electrode 25 can be cancelled at the storagecapacitor bus line 18. Therefore, the alignment orientation of theliquid crystals 6 near the storage capacitor part 21 can be aligned withthe orientation controlled by the micro slits 30 a and 30 b. Since thedirection (arrow) of the oblique electric field is controlled in thedirection in which the electric field is stronger, the oblique electricfield is generated in the direction in which the distance between theelectrodes is short in the case in which the potential is almost thesame as with the storage capacitor bus line 18 and the common electrode41. Accordingly, the oblique electric field of the control capacitanceelectrode 25 can be suppressed from being generated outside the storagecapacitor part 21.

The cross section near the backbone part 26 in the pixel layout shown inFIG. 15 is as shown in FIG. 13. On the glass substrate 10 of the TFTsubstrate 2, the gate insulating film 31, the control capacitanceelectrode 25, the final protective film 32, the pixel electrode 16, andthe vertical alignment film 33 are sequentially formed, and on the glasssubstrate 11 of the opposite substrate 4, the BM 50, the color filterlayer 40, the common electrode 41, and the vertical alignment film 33are sequentially formed.

As in (2) above, the control capacitance electrode 25 is formed insidethe pixel electrode 16, and thus the oblique electric field of thecontrol capacitance electrode 25 can be cancelled at the pixel electrode16. Thus, the alignment orientation of the liquid crystals 6 near thebackbone part 26 formed by the control capacitance electrode 25 and thepixel electrode 16 can be aligned with the orientation controlled by themicro slits 30 a and 30 b. In the case in which a potential differenceexists as with the pixel electrode 16 and the common electrode 41, thecontrol capacitance electrode 25 is shielded by the pixel electrode 16,and thus the oblique electric field of the control capacitance electrode25 can be suppressed from being generated outside the pixel electrode16.

As in (3) above, the alignment orientation of the liquid crystals 6 issplit at the border of the control capacitance electrode 25 or thestorage capacitor bus line 18, the alignment border of the liquidcrystals 6 at which the φ fluctuations are relatively great can beshielded by the control capacitance electrode 25 or the storagecapacitor bus line 18, and thus the φ fluctuations can be seemingly madesmall.

As in (4) above, the direct coupling part 16 a of the pixel electrode 16is formed on the source electrode 22 side of the TFT 20, and thus thepotential difference between the source electrode 22 and the pixelelectrode 16 near the TFT 20 can be eliminated. Therefore, the alignmentorientation of the liquid crystals 6 near the TFT 20 can be aligned withthe orientation controlled by the micro slits 30 a and 30 b.

As in (5) above, the pixel electrode 16 is removed from the area facingthe resin spacer 52 formed on the opposite substrate 4, and thus it canbe eliminated that the resin spacer 52 distorts the oblique electricfield of the pixel electrode 16. Therefore, the alignment orientation ofthe liquid crystals 6 near the resin spacer 52 can be aligned with theorientation controlled by the micro slits 30 a and 30 b.

Example 2-2

FIG. 19 shows the pixel configuration of a liquid crystal display deviceaccording to the example 2-2 of the embodiment, and FIG. 20 shows thepixel alignment of the liquid crystal display device according to theexample. As shown in FIG. 19, in the example, a direct coupling part 16a and a capacitive coupling part 16 b are isolated from each other atthe border of a storage capacitor part 21, and light at the part of thepixel electrodes 16 a and 16 b adjacent to the storage capacitor part 21is shielded by a BM 50 which is formed on a opposite substrate 4. Theconfiguration in the example is almost the same as that of the example2-1 except the BM 50.

In the example 2-1 and the comparative example 2-1, light in the areaadjacent to the gate bus line 12 or the drain bus line 14 is shieldedfor cross talk measures, but light in the area adjacent to the storagecapacitor part 21 is not shielded because that area is not involved incross talk measures. However, in the examples 2-1 and 2-2, the directcoupling part 16 a and the capacitive coupling part 16 b are isolatedfrom each other at the border of the storage capacitor part 21, and thusthe area adjacent to the storage capacitor part 21 is the pixelelectrode end as similar to the area adjacent to the gate bus line 12 orthe drain bus line 14. Therefore, the φ fluctuations near the storagecapacitor part 21 are relatively great. As compared with the pixelalignment of the example 2-1 shown in FIG. 16, in the pixel alignment ofthe example shown in FIG. 20, the dark line in the area adjacent to thestorage capacitor part 21 is as small as that in the area adjacent tothe gate bus line 12 or the drain bus line 14.

Pixel Evaluation in Examples 2-1 and 2-2

FIG. 21 is a graph illustrating the azimuth angle distributions of thealignment of liquid crystals of the liquid crystal display devices ofthe examples 2-1 and 2-2 and the comparative example 2-1. The azimuthangle distribution is that the average value at the azimuth angle isdetermined by computation when an area is scanned in the horizontal (x)direction from the BM end to the backbone end, the area surrounded by athick line in FIGS. 16, 18 and 20 in which the micro slits 30 a and 30 bare extended in the azimuth angle of 225 degrees. It shows that when theaverage value of the azimuth angle is greatly shifted from the angle of225 degrees, the φ fluctuations of the alignment of liquid crystals aregreater.

As shown in FIG. 21, in the comparative example 2-1, since great φfluctuations are generated in the border area between the directcoupling part 16 a and the capacitive coupling part 16 b, the averagevalue of the azimuth angle is also greatly shifted from the azimuthangle of 225 degrees controlled by the micro slits 30 a and 30 b. On theother hand, in the examples 2-1 and 2-2, those φ fluctuations areremoved, and thus the shift is made small. In addition, in the example2-2, light is shielded in the area in which the φ fluctuations arerelatively great by the BM 50, and thus the shift is smaller than thatin the example 2-1.

FIG. 22 shows a graph illustrating the gray level γ characteristic inthe oblique direction in the liquid crystal display devices of theexamples 2-1 and 2-2 and the comparative example 2-1. The gray level γcharacteristic is determined by actually measuring the γ value at everygray level at the position in the horizontal direction and tilted at anangle of 60 degrees from the substrate normal for the entire pixel area.It shows that when the γ value is greatly shifted from a set value onthe front side, the color shift becomes greater in that direction.

As shown in FIG. 22, in the comparative example 2-1, great φfluctuations are generated in the border area between the directcoupling part 16 a and the capacitive coupling part 16 b, and thus the γvalue is greatly shifted from a set value on the front side particularlyon the high gray level side. On the other hand, in the examples 2-1 and2-2, those φ fluctuations are removed, and thus the shift is made small.In addition, in the example 2-2, light is shielded in the area in whichthe φ fluctuations are relatively great by the BM 50, and thus the shiftis made smaller than that in the example 2-1.

Example 2-3

FIG. 23 shows the pixel configuration of a liquid crystal display deviceaccording to example 2-3 of the embodiment, and FIG. 24 shows the pixelalignment of the liquid crystal display device according to the example.As shown in FIG. 23, in the example, a direct coupling part 16 a and acapacitive coupling part 16 b are isolated from each other at the borderof a storage capacitor part 21, and the direction in which micro slits30 a and 30 b are extended adjacent to a gate bus line 12 or a drain busline 14 is almost vertical to the direction in which the gate bus line12 or the drain bus line 14 is extended. The example has almost the sameconfiguration as that of the example 2-1 except the direction in whichthe micro slits 30 a and 30 b are extended and the shape of a controlcapacitance electrode 25. However in the example, the direction in whichthe micro slits 30 a and 30 b are extended is almost vertical to thedirection in which the gate bus line 12 or the drain bus line 14 isextended and the shape of the backbone part is also changed inaccordance therewith, and thus the shape of the control capacitanceelectrode 25 is correspondingly modified.

In the comparative example 2-1, and the examples 2-1 and 2-2, since thedirection in which the micro slits 30 a and 30 b are extended is tiltedat an angle of 45 degrees with respect to the gate bus line 12 or thedrain bus line 14, the direction of the oblique electric field of thepixel electrode is shifted from the direction of the oblique electricfield of the pixel space at an angle of 45 degrees. On the other hand,in the example 2-3, since the direction in which the micro slits 30 aand 30 b are extended is almost vertical to the direction in which thegate bus line 12 or the drain bus line 14 is extended, the direction ofthe oblique electric field of the pixel electrode and the direction ofthe oblique electric field of the pixel space are almost the samedirection, and the alignment orientation of the liquid crystals 6 nearthe gate bus line 12 or the drain bus line 14 can be aligned with theorientation controlled by the micro slits 30 a and 30 b. Here, thereason why the direction in which the micro slits 30 a and 30 b areextended is almost vertical to the direction in which the gate bus line12 or the drain bus line 14 is extended is that the pixel space works asa slit of wide width to generate an oblique electric field vertical tothe gate bus line 12 or the drain bus line 14.

In addition, when the pixel alignments of the comparative example 2-1,and the examples 2-1 and 2-2 are compared with the pixel alignment ofthe example shown in FIG. 24, in the example, the dark line near thegate bus line 12 or the drain bus line 14 is obviously small, and it isrevealed that no problem arises even though light is not shielded in apart of the pixel electrode near the storage capacitor part 21 by the BM50.

Pixel Evaluation in Example 2-3

FIG. 25 shows a graph illustrating the azimuth angle distribution of thealignment of liquid crystals of the liquid crystal display deviceaccording to the example 2-3. The azimuth angle distribution is that theaverage value at the azimuth angle is determined by computation when anarea is scanned in the horizontal (x) direction, the area surrounded bya thick line in FIG. 24 in which the micro slits 30 a and 30 b areextended in the azimuth angle of 180 degrees. It shows that when theaverage value of the azimuth angle is greatly shifted from the angle of180 degrees, the φ fluctuations of the alignment of liquid crystals aregreater.

As shown in FIG. 25, in the example 2-3, the φ fluctuations almost thesame as those in the examples 2-1 and 2-2 are generated near thebackbone part, but the φ fluctuations are removed at the BM end at whichthe greatest φ fluctuations are generated in the comparative example2-1, and the examples 2-1 and 2-2.

FIG. 26 shows a graph illustrating the gray level γ characteristic ofthe liquid crystal display devices in the oblique direction according tothe comparative example 2-1 and the example 2-3. The gray level γcharacteristic is determined by actually measuring the γ value at everygray level at the position in the horizontal direction and tilted at anangle of 60 degrees from the substrate normal for the entire pixel area.It shows that when the γ value is greatly shifted from a set value onthe front side, the color shift becomes greater in that direction.

As shown in FIG. 26, in the comparative example 2-1, great φfluctuations are generated in the border area between the directcoupling part 16 a and the capacitive coupling part 16 b, and thus the γvalue is greatly shifted from a set value on the front side particularlyon the high gray level side. On the other hand, in the example 2-3,those φ fluctuations are removed, and thus the shift is made small. Inaddition, as compared with the examples 2-1 and 2-2, the example 2-3 hasthe smallest shift of the γ value in the entire gray levels.

Third Embodiment

Next, a liquid crystal display device according to a third embodiment ofthe invention will be described with reference to FIGS. 27 to 33. FIG.27 shows the pixel configuration of a liquid crystal display devicewhich can vary the voltage applied to the liquid crystals in a singlepixel. As shown in FIG. 27, a pixel electrode 16 has a direct couplingpart 16 a which is directly connected to a source electrode of a TFT 20,and a capacitive coupling part 16 b which is connected to the sourceelectrode through capacitance. For example, a micro slit is formed bothin the direct coupling part 16 a and the capacitive coupling part 16 b,and monomers are polymerized with voltage applied to liquid crystals.Thus, a liquid crystal display device of an excellent displaycharacteristic can be obtained.

FIGS. 28A to 28C schematically show process steps of polymerizingmonomers mixed in liquid crystals. In polymerizing monomers 61 shown inFIG. 28A, voltage is applied to the liquid crystals to tilt liquidcrystals molecules 60 and the monomer 61 in a predetermined directionfor irradiating UV light (FIG. 28B). The monomers 61 are polymerized bythe UV light, and polymer main chains 62 are formed on the interface ofa substrate 63 (FIG. 28C). Thus, the tilt orientation of the liquidcrystals molecules 60 is stored.

However, in the area on the control capacitance electrode 25, sufficientUV light cannot be irradiated onto the liquid crystals. Therefore, sincemonomer polymerization is insufficient and the alignment control isweaker than that in the other areas, a problem arises that the alignmentof the liquid crystals is unstable and the response speed is slow (theresponse time is prolonged).

The embodiment is made to solve the problem, and an object is to providea liquid crystal display device which has an excellent response ofliquid crystals and bright display.

The object is achieved by a liquid crystal display device including:sandwiching liquid crystals containing polymerizable monomers between afirst substrate provided with a pixel electrode having a micro slit anda second substrate facing the first substrate; polymerizing the monomersas voltage is applied to the liquid crystals; and controlling analignment orientation of the liquid crystals to a direction in which themicro slit is extended, wherein the pixel electrode includes: a directcoupling part which is electrically connected to a switching element;and a capacitive coupling part which is electrically insulated from theswitching element, and which forms capacitance with a controlcapacitance electrode which has a same potential as that of a sourceelectrode of the switching element, wherein the capacitive coupling parthas an electrode open part which is disposed in a border between splitareas of the alignment of liquid crystals, and the control capacitanceelectrode is disposed below the electrode open part.

In the liquid crystal display device according to the embodiment, theelectrode open part has a width equal to or greater than one fourth of acell thickness.

In the liquid crystal display device according to the embodiment, theelectrode open part has a cross shape.

In the liquid crystal display device according to the embodiment, a sideof the electrode open part facing the micro slit is almost vertical to adirection in which the micro slit is extended.

FIG. 29 shows a diagram illustrating the basic pixel configuration of aliquid crystal display device according to the embodiment. As shown inFIG. 29, a pixel electrode 16 has a direct coupling part 16 a which iselectrically connected to a source electrode of a TFT 20, and acapacitive coupling part 16 b which is electrically isolated from thedirect coupling part 16 a and forms capacitance with a controlcapacitance electrode 25 which is the same potential as that of thesource electrode of the TFT 20. At the border of the liquid crystalalignment split area in the capacitive coupling part 16 b (for example,the intersection point of alignment split lines), an electrode open part70 is formed in which the pixel electrode 16 is partially removed. Belowthe electrode open part 70, the control capacitance electrode 25 ispartially disposed.

A potential difference is generated between the capacitive coupling part16 b of the pixel electrode 16 and the control capacitance electrode 25.The electrode open part 70 having the control capacitance electrode 25therebelow is disposed in the border between the alignment split areas,and thus the orientation of tilting the liquid crystals molecules at thepixel edge is equal to the orientation of tilting the liquid crystalsmolecules at the electrode open part 70 when voltage is applied.Therefore, the alignment of liquid crystals in the border between thealignment split areas quickly becomes stable. However, when theelectrode open part is disposed at the position at which the controlcapacitance electrode 25 is not disposed in the lower layer, theorientation of tilting the liquid crystals molecules at the electrodeopen part is reverse to the orientation of tilting the liquid crystalsmolecules at the pixel edge. Thus, the alignment in the border betweenthe alignment split areas becomes unstable.

Hereinafter, the liquid crystal display device according to theembodiment will be described more specifically with examples.

Example 3-1

A TFT substrate having the pixel configuration shown in FIG. 29 wasprepared. The TFT substrate and a opposite substrate were bondedtogether to have a cell thickness of 4.25 μm, negative liquid crystals Aproduced by Merck Ltd., which had polymerization monomers dissolved weresealed between the substrates, and a liquid crystal display panel wasprepared which was 15 inches diagonally. The liquid crystal displaypanel prepared was annealed at a temperature of 90° C. for 30 minutes.After cooled, 5000 mJ of no polarized ultraviolet rays includingwavelengths of 300 to 400 nm were irradiated while 20 V of AC voltagewas applied to the liquid crystals. As the result of observing thealignment of liquid crystals, it was confirmed that the alignment in asingle pixel was split into four parts.

FIG. 30A shows the alignment state near the alignment split area of thepixel of a liquid crystal display panel according to the embodiment.FIG. 30B shows the alignment state of a liquid crystal display panelaccording to a comparative example in which no electrode open part 70 isdisposed. As shown in FIGS. 30A and 30B, in the liquid crystal displaydevice according to the embodiment, the electrode open part 70 wasdisposed to obtain a stable alignment of liquid crystals.

The relationship between the presence of the electrode open part 70 andthe response speed (response time) was studied. In the liquid crystaldisplay panel according to the example in which the electrode open part70 was disposed, the response time was shorter than that of the liquidcrystal display panel having no electrode open part 70. Here, theresponse time is defined by the sum of the rise time (τr) of 10 to 90%of the transmittance intensity of write (white) voltage and the falltime (τr) of 90 to 10% of that.

Example 3-2

In a liquid crystal display panels prepared by almost the same processsteps as those of the example 3-1, the relationship between the width ofthe electrode open part 70 and the response time was studied. FIG. 31shows the relationship between the electrode open part 70 and the equalpotential line. As shown in FIG. 31, when the width of the electrodeopen part 70 equals or is greater than one fourth of a cell thickness,the orientation of tilting the liquid crystals molecules 60 at the pixeledge is equal to the orientation of tilting the liquid crystalsmolecules 60 at the electrode open part 70. On the other hand, when thewidth of the electrode open part 70 is below one fourth of a cellthickness, the orientation of tilting the liquid crystals molecules 60at the pixel edge is in reverse to the orientation of tilting the liquidcrystals molecules 60 at the electrode open part 70.

When the relationship between the width of the electrode open part 70and the response time was studied, the response time of a liquid crystaldisplay panel provided with an electrode open part 70 having a widthsmaller than one fourth of a cell thickness had almost the same responsetime of a liquid crystal display panel provided with no electrode openpart 70. On the other hand, in a liquid crystal display panel providedwith an electrode open part 70 having a width equal to or greater thanone fourth of a cell thickness, the response time was more shortenedthan that of the liquid crystal display panel provided with no electrodeopen part 70.

Example 3-3

In a liquid crystal display panels prepared by almost the same processsteps as those of the example 3-1, the relationship between the shapeand the response time of the electrode open part 70 was studied. In theconfiguration shown in FIG. 32, an electrode open part 70 has a crossshape which is extended along the border between the alignment splitareas. In the configuration shown in FIG. 33, an electrode open part 70has an almost square shape, and its four sides are almost vertical tothe directions in which micro slits 30 b facing thereto are extended.

When the relationship between the shape of the electrode open part 70and the response time was studied, it was revealed that the electrodeopen parts 70 in the shapes shown in FIGS. 32 and 33 were formed tofurther shorten the response time than that of the liquid crystaldisplay panel according to the example 3-1.

The invention can be modified variously, and not limited to theembodiments.

For example, the transmissive liquid crystal display device is taken asan example in the embodiments, but the invention is not limited thereto,and can be adapted to the other liquid crystal display devices such as areflective type and a transflective type.

1. A liquid crystal display device comprising: liquid crystals havingnegative dielectric anisotropy and are vertically aligned when voltageis not applied between a first substrate provided with a pixel electrodehaving micro slits and a second substrate facing the first substrate;and an alignment orientation of the liquid crystals is controllable to adirection in which the micro slits are extended, wherein the pixelelectrode includes: a direct coupling part which is electricallyconnected to a switching element; and a capacitive coupling part whichis electrically insulated from the switching element, and which formscapacitance with a control capacitance electrode which has a samepotential as that of a source electrode of the switching element,wherein a smaller voltage is applied to the capacitive coupling partwhen the capacitive coupling part is driven than that to the directcoupling part, wherein the direct coupling part and the capacitivecoupling part are isolated from each other at a border of the controlcapacitance electrode and/or a storage capacitor bus line.
 2. The liquidcrystal display device according to claim 1, further comprising: analignment film formed on the first substrate or the second substrate;and a polymerized film formed on an interface of the alignment film. 3.The liquid crystal display device according to claim 1, wherein in anarea in which the control capacitance electrode and the storagecapacitor bus line overlap with each other, the control capacitanceelectrode is disposed inside the storage capacitor bus line.
 4. Theliquid crystal display device according to claim 1, wherein in an areain which the control capacitance electrode and the pixel electrodeoverlap with each other, the control capacitance electrode is disposedinside the pixel electrode.
 5. The liquid crystal display deviceaccording to claim 1, wherein the alignment orientation of the liquidcrystals is split at a border of the control capacitance electrode orthe storage capacitor bus line.
 6. The liquid crystal display deviceaccording to claim 1, wherein the direction in which the micro slits areextended as adjacent to the gate bus line or the drain bus line isalmost vertical to a direction in which the gate bus line or the drainbus line is extended.
 7. The liquid crystal display device according toclaim 1, wherein the direct coupling part of the pixel electrode isdisposed on a source electrode side of the switching element.
 8. Theliquid crystal display device according to claim 1, wherein the pixelelectrode is not formed in an area facing a resin spacer which is formedon the second substrate.
 9. The liquid crystal display device accordingto claim 1, wherein light is shielded in a part adjacent to the controlcapacitance electrode and/or the storage capacitor bus line in the pixelelectrode by a black matrix which is formed on the second substrate.